Dynamo-electric machine



June 21, 1938. k, BOBEK 2,121, 23

DYNAMO-ELECTRIG MACHINE Filed June 5, 1936 Fig. I.

Invehtov: K014 BObek, y y x M Hi Attovneg.

Patented June 21, 1938 UNITED STATES PATENT GFFIC E General ElectricCompany,

New York a corporation of Application June 3, 1936, Serial No. 83,378

In Germany June 8, 1935 2 Claims.

My invention relates to improvements in dynamo-electric machines andparticularly to ventilating systems for machines wherein both thearmature and field are rotatably mounted.

One of the most common applications of dynamo-electric machines havingboth the armature-and field rotatably mounted is in connection withelectric dynamometers. These dynamometers are usually of the cradle typeand are frequently required to operate over a very wide range of speed.The internal ventilation of such machines is very small for low speedsand frequently is insuflicient to prevent overheating unless an externalventilating system is used which is independent of the speed of themachine. In former practice, external ventilators have been used whichare attached to the outer rotatable member, but such an arrangement hasthe disadvantage that the ventilating equipment is carried by theexternal rotatable member and affects the sensitivity of the machine. Inorder to eliminate this difficulty, ventilators have been provided whichare mounted independent of the external rotatable member and areconnected Q5 thereto by a flexible connection in the form of a flexibletubing or the like, but such a flexible conneotion also tends to exert adamping effect on the sensitivity of the machine.

An object of my invention is to provide a dynamo-electric machinewherein both the armature and field structure are rotatably mounted anda ventilating system is provided which substantially does not interferewith the sensitivity or operation of the machine.

Further objects and advantages of my invention will become apparent, andmy invention will be better understood, from the following descriptionreferring to the accompanying drawing, and the features of novelty whichcharacterize my invention will be pointed out with particularity to theclaims annexed to and forming a part of this specification.

In the drawing, Fig. 1 is a side elevation of a cradle dynamometerprovided with my improved 45 ventilating system, the stationaryventilating casing being shown in section; Fig. 2 is an end elevation ofthe machine illustrated in Fig. 1; and Fig. 3 is a fragmentary sectionalview of a flanged labyrinth joint between the stationary ventilatingcasing and the rotatable machine frame.

Referring to the drawing, I have illustrated a dynamo-electric machineincluding an armature 10 provided with a commutator H and brushes l2.The armature is mounted on a shaft [3 which is rotatably supported inbearings arranged in upright arms l4 and I5 of a mounting base it. Afieldstructure including a frame ill is arranged to cooperateelectrodynamically with the armature iii, and also is rotatably or'movably supported in bearings mounted in the upright arms M and iii ofthe mounting base it. The rotational. movement of the field framestructure ii is limited by 2. lug l8 secured to the end shield it on oneend of the field frame structure and extends between two limit stops 2%?secured to the vertical arm l5 of the mounting base.

A dynamometer lever arm 2| is secured by a mounting plate 22 to one sideof the field frame structure H. 'A reverse torque mechanism connects theouter end of the lever arm 2| to a force measuring device. This reversetorque mechanism includes a bar 23 secured to the end of the lever arm2|, and each of the ends of the bar 23 is provided with a notch arrangedto engage with pivot pins 24 and 25 of the reverse torque mechanism. Ifthe torque on the field frame I! is in a counter-clockwise direction, asviewed in Fig. 2, the notch 24' in the bar 23'Will engage pin 24 andwill exert a downward pull on a link 26 which is connected at 2'! to aspring balance scale 28 and a balance mechanism 29. The balancemechanism is pivotally suspended at 36 from a supporting bar 3| mountedupon vertical supports 32, which are secured to the mounting base It. Ifthe torque on the field frame structure I? is in a clockwise direction,as viewed in Fig. 2, the notch 24' in the bar 23 will become disengagedfrom the pin 24 and the bottom of the notch 25' will press upwardlyagainst the pin 25 and exert an upward force upon a link 33. The lowerend of the link 33 will engage a pin 34, which is secured to one end ofa bar 35 pivotally supported at 38 on a threaded bar 36a secured to themounting base I 6. The up ward force transmitted to the linkage 33 bythe bar 23 will be transmitted through the pivoted bar 35 and acorresponding downward force will be exerted by a pin 3'! secured to theother end of the bar 35. The pin 3! will engage the lower portion of alost motion slot 38 in the link 26 and exert a downward pull upon thespring scale 28 and the balance mechanism 29. In this manner, bothclockwise and counter-clockwise torques will give positive indicationsupon the force measuring device including the spring scale 28 and thebalance mechanism 29.

In order to provide for the proper ventilation of the dynamo-electricmachine, ventilating openlugs 39 are formed adjacent one end of thefield frame H. A stationary casing 40 is mounted closely adjacent theother end of the field frame l1, and is separated therefrom by a verysmall clearance 4|, just sufficient to permit free turning of the fieldframe ll with respect to the casing 40. This casing 40 is formed with anopening in one side thereof which communicates with the interior of thefield frame structure l1, and it is supported upon the upright arm I4 bybolts 44 and 45. A cooling and ventilating medium, such as air, is blownthrough the casing 4|] and into the field structure U, as indicated bythe arrows 41 in Fig. 2, by a fan mounted in a casing 48. The fan isdriven by an electric motor 49 and both are rigidly secured to themounting base l6, as shown in Fig. 2.

In certain instances, it may be desired to provide a better seal thanthat illustrated in Fig. 1, and in such cases a labyrinth flanged seal,as shown in Fig. 3, may be used. This flanged seal includes an axiallyextending circumferential flange 50 formed around the circumference ofthe end of the field frame H. A radially extending flange 5| is formedon the ventilating casing 40 and is provided with an axially extendingcircumferential groove 52 which is arranged to cooperate and extendabout the flange 50. A very small clearance is provided between theflange 50 and the groove 52, in order to provide for free movement ofthe frame l1 with respect to the casing 40 and to minimize leakage ofventilating medium about the flange 5D.

Modifications of the embodiments of my invention, which I haveillustrated and described,

will occur to those skilled in the art. I desire it to be understood,therefore, that my invention is not to be limited to the particulararrangements disclosed, and I intend in the appended claims to cover allmodifications which do not depart from the spirit and scope of myinvention.

What I claim as new and desire to secure by Letters Patent is:

1. A dynamo-electric machine having a rotatable member, a second membermovably mounted about said rotatable member and arranged to cooperateelectrodynamically therewith, means including a stationary casing havingan opening communicating with said movable member for supplying acooling medium thereto, and a labyrinth flanged seal arranged betweensaid stationary casing and said movably mounted member.

2. A dynamo-electric machine having a rotatable member, a second memberhaving a ventilating opening adjacent one end thereof mounted forlimited rotational movement about said first mentioned rotatable memberand arranged to cooperate electrodynamically therewith, means connectedto said second rotatable member for measuring the torque exertedthereby, a mounting base arranged to rotatably support saiddynamo-electric machine, a stationary casing secured to said mountingbase and arranged closely adjacent the other end of said secondrotatable member and having an opening communicating therewith, a

labyrinth flanged seal arranged between said stationary casing and saidsecond rotatable member, and means for supplying a ventilating medium tosaid dynamo-electric machine through said stationary casing.

KARL BOBEK.

